Display device and method of fabricating the same

A method of fabricating a display device, the method comprising:

• forming a crystalline silicon pattern on a substrate;
• forming an upper gate insulating film on the crystalline silicon pattern;
• and
• dividing the crystalline silicon pattern into a lower gate insulating film and an active layer disposed on the lower gate insulating film, the active layer including crystalline silicon, the dividing of the crystalline silicon pattern including:
• forming the active layer above the lower gate insulating film to completely cover an upper surface of the lower gate insulating film;
• and
• aligning at least one of sidewalls of the active layer with at least one of sidewalls of the lower gate insulating film,
• wherein the dividing of the crystalline silicon pattern includes:
• implanting oxygen into a lower portion of the crystalline silicon pattern;
• and
• dividing the lower portion of the crystalline silicon pattern from an upper portion of the crystalline silicon pattern by forming the lower portion of the crystalline silicon pattern as the lower gate insulating film through heat treatment, the upper portion of the crystalline silicon pattern being the active layer including the crystalline silicon.